1. Technical Field
The invention relates to the field of portable resin dispensers and, in particular, to pistol types using solid tubular shaped resin rods which are melted prior to application.
2. Description of the Related Art
When assembling thermoplastic composite parts for subsequent forming into a single integral assembly, it is often necessary to precisely locate the parts and hold them in place during the molding process, such as in the step of vacuum bagging and the like. This is easily accomplished by tack welding using a thermoplastic filler rod. When making field repairs to a composite structure, the filling of cavities or cracks is also easily accomplished using portable resin dispensers. These are just two of the applications for portable resin dispensers which can accurately apply melted resin in precise amounts to a surface.
Portable resin dispensers are quite common and are usually in the shape of pistols. The most notable is the portable glue gun wherein a rod of glue is loaded from the back end and sequentially advanced by the pull of a trigger. A resistance heating coil is mounted in the barrel and activated to melt the glue or at least heat it to a point wherein it becomes a paste that can be easily applied to a surface. A more sophisticated version can be found in U.S. Pat. No. 4,647,158 "Hot Glue Pistol" by Sternel et al. Here, there is no heating coil, but a separate blower which is used to direct hot air to the bonding location. The blower incorporates a nozzle assembly which is used to direct hot air to the bonding location. The nozzle also supports the glue gun portion and heats the glue to its melting temperature by conduction. While this device would work well with low temperature glue, its use with high temperature thermoplastic resins, with melting points in the 700.degree. F. range, would create problems. For example, there would be a lag in raising the thermoplastic resin to the melting temperature due to the need to conduct heat through the nozzle structure. Furthermore, the heat transferred to the glue gun portion would be so great that it would tend to melt the whole resin rod. Also of interest is U.S. Pat. No. 4,260,439 "Apparatus and Method for Repairing Plastic Materials" by Speer which discloses a hot air gun for curing vinal upholstery material. Powdered vinal is placed on the spot to be repaired and hot air is ejected from a nozzle which melts the vinal into the tear or the like. This apparatus is not readily applicable to the task at hand, since it would be extremely difficult to precisely locate powdered thermoplastic resin precisely and maintain it in position when tacking structural parts together prior to forming a complicated structure.
Thus, it is a primary object of the subject invention to provide a portable resin dispenser capable of applying melted resin at a precise location.
It is a still further object of the subject invention to provide a portable resin dispenser that can preheat the surface prior to the application of melted resin so as to provide a superior bond.
It is a still further object of the subject invention to provide a portable resin dispenser for dispensing thermoplastics having melting temperatures in the 700.degree. F. range.